The present invention relates to pedestals for providing angular motion, and in particular to pedestals for antennas. Still more specifically, the present invention relates to antenna pedestals for providing X-Y antenna displacements.
X-Y antennas are well known and are valuable for many applications. However, typical X-Y pedestals have a very high profile, large sweep volume, and limited sky coverage. These characteristics of the prior art X-Y pedestals have limited the applicability of X-Y axis pedestal antennas.
For example, prior art X-Y antennas are caused to rotate about a single X axis pivot and a single Y axis pivot such that, if simple linear actuators are to be used to produce rotative movement, the resultant geometric configurations are necessarily of a high profile and the antenna must sweep a relatively large volume, while the positioning of the X and Y axis with respect to its associated actuators limits sky coverage to sweeps of 90.degree. in either direction with respect to the X and Y axes.
Accordingly, it is an object of the present invention to provide an X-Y antenna pedestal for providing angular motion that permits extended sky coverage.
It is also an object of this invention to avoid the above-noted disadvantages by providing an X-Y axis pedestal which enables a low profile to be obtained with respect to each of the axes.
It is a still further object of the present invention to achieve all of the above-noted objects in a pedestal construction which is driven by simple actuators and wherein the structural configuration is such that fabrication costs are lowered, and the pedestal can be easily assembled on site from a few compact units.
The above and other objects of the invention are achieved according to a preferred embodiment of the present invention by constructing the pedestal of a base, lower subassembly and upper subassembly.
To provide angular displacement with respect to the base, a pair of parallel rotational axes are positioned between the base and the lower subassembly, and a pair of linear actuators are connected between the base and the lower subassembly for angularly displacing the subassembly about the pair of parallel axes through two separate arc sectors which are located in a common plane so as to enable an antenna mounted upon the pedestal to be swept through arcs of, for example, .+-.125.degree..
Additionaly, the upper subassembly is mounted so as to be angularly displaceable with respect to the lower subassembly by the provision of a second pair of parallel axes between the upper and lower subassemblies, this further pair of axes being oriented in an orthogonal manner with respect to the axes located between the base and lower subassembly, such that if the first pair of axes serve as the X-axis, the second set of axes between the upper and lower subassemblies will serve as the Y-axis. In a preferred embodiment the linear actuators for angularly displacing the upper and lower subassemblies are constructed in a simple manner, for example, through the use of a pair of linear actuators, such as fluid driven piston-cylinder units arranged diagonally for driving a respective pedestal about a respective axis.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.